Generate optimizer func info from stubs for a few extensions - part 2 (#7401)

ext/bcmath, ext/fileinfo, ext/filter, ext/gettext, ext/session

Use single line phpdoc in stubs where possible

Not serializable flag permeation

Declare tentative return types for ext/fileinfo

Relates to GH-6985

Merge branch 'PHP-8.0'

* PHP-8.0:
Make finfo_open() $magic_database nullable

Make finfo_open() $magic_database nullable

Empty string was interpreted as a special value here, which indicates
that the default magic database should be used. It makes more sense
t

Make finfo_open() $magic_database nullable

Empty string was interpreted as a special value here, which indicates
that the default magic database should be used. It makes more sense
to use null for this purpose.

The documentation also explicitly mentions that null can be used.

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Implicitly enable function entry generation when class entry generation is enabled

Closes GH-6675

Generate class entries from stubs for another batch of extensions

Closes GH-6669

Convert file_info resources to objects

Besides our general desire to get rid of the legacy resource types,
this is particularly appealing for fileinfo, because there are already
resp

Convert file_info resources to objects

Besides our general desire to get rid of the legacy resource types,
this is particularly appealing for fileinfo, because there are already
respective objects.

Closes GH-5987.

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Update fileinfo parameter names

Closes GH-6206.

Fix nullable types in PHPDoc

Generate method entries from stubs for a couple of extensions

Closes GH-5368

Add missing visibility modifiers in stubs

Generate function entries from stubs for a couple of extensions

Closes GH-5347

Add union return types for function stubs

Convert fileinfo functions arginfo to php stubs

We also allow the context for finfo to be null.